To deploy a wireless communication network, an operator needs to invest very high costs in an initial stage. The 2nd generation (2G) mobile communication network global system of mobile communication/enhanced data rate for GSM evolution (GSM/EDGE) has been successful in commercial usage globally for many years. With large-scale deployment and commercial usage of the 3rd generation (3G) mobile communication network universal mobile telecommunications system (UMTS) and hotspot deployment of the 4th generation (4G) mobile communication network long term evolution (LTE), operators, especially some new operators, gradually give up conventional strategies to deploy their own networks separately, and turn to build shared networks with other operators or to rent networks already deployed by other operators, in order to save the costs for network deployment and operations, to speed up the network deployment, and to expand the nextwork coverage.
Currently, there are mainly two ways for network sharing.
In the first way, at least two mobile operators share a radio access network (RAN) and mobility management network elements in core network, such as mobile switching center (MSC), serving GPRS support node (SGSN) and mobility management entity (MME), while other core network elements are not shared.
In the second way, at least two mobile operators share only the RAN, i.e., the mobility management network elements in core network are not shared.
Generally, a user equipment (UE) resides in its home public land mobile network (HPLMN) or equivalent HPLMN network (EHPLMN), and register itself at its HPLMN or EHPLMN to provide services to users. In some cases, for example, if a user roams to another country/region, or a place without signal coverage of a home operator, then the UE needs to select a visited public land mobile network (VPLMN), and at this time the UE is in a roaming state.
There are two network selection modes as follows for an idle mode UE to select a network in a shared cell.
In an automatic network selection mode, a UE is preconfigured with a PLMN list, where the PLMNs in the list are sorted by priority, and the UE automatically selects an available network with highest priority according to the PLMN list when network selection is desired, where the automatic network selection needs no participation of a user and the user has no perception of the selection.
In a manual network selection mode, a UE displays all currently available networks to a user, and the user manually selects a desired network.
For a UE residing in its HPLMN or EHPLMN, the HPLMN/EHPLMN of the UE has highest priority. Whereas for a UE residing in a VPLMN and adopting the automatic network selection mode, the current registered public land mobile network (RPLMN) of the UE does not necessarily have the highest priority. In order to avoid communication interruption or delay caused by the frequent network reselection of the UE in roaming state, the UE still prefers to select the current RPLMN rather than performs network selection if the current RPLMN is available in a current cell.
However, if a UE resides in a VPLMN and the UE is already within coverage of the UE's home HPLMN or EHPLMN, then the UE still resides in the VPLMN and is in a roaming state because the current RPLMN is still available in the current cell. Thus, user's requirements for a stable and reliable local service (non-roaming service) with higher quality at low charges can not be met, and the user's experience is poor. Similarly, if a UE resides in a VPLMN and the UE is already within coverage of a PLMN with higher priority, then the UE still resides in the VPLMN with lower priority because the current RPLMN is still available in the current cell. Thus, user's requirements for stable and reliable service with higher quality can not be met, which results in poor user experience as well.